Industrial water systems are commonly chemically treated to minimize corrosion and reduce deposition along those metal surfaces in contact with the aqueous medium. Typical treatment programs include those disclosed in, inter alia, U.S. Pat. No. 3,837,803 (Vogt et al) and U.S. Pat. No. 4,029,577 (Godlewski et al).
One particularly troublesome fouling species is iron based fouling that typically occurs in water systems being supplied with water from an iron containing well water source. One successful approach in treating such conditions has been disclosed in U.S. Pat. No. 4,387,027 (May et al).
Well waters typically exist under reducing conditions. Under such conditions, iron exists primarily as the ferrous ion (Fe.sup.+2) species. Upon exposure to air, the ferrous ion oxidizes to ferric ion (Fe.sup.+3). The ferrous ion is typically present as the aquo ion, Fe(H.sub.2 O).sub.6.sup.+2, while the ferric ion exists as a hydrated oxide, Fe.sub.2 O.sub.3..sub.n H.sub.2 O. From known solubility data, the Fe.sup.+2 ion is 10.sup.15 times more soluble at pH 7 than is the Fe.sup.+3 ion. Accordingly, iron is soluble in well water (as Fe.sup.+2). Upon exposure to air (as would be encountered when such well water is admitted to a cooling water system), this freshly produced iron species (Fe.sup.+3) becomes almost completely insoluble and is the root of a most troublesome fouling problem.
In those instances in which water soluble polymers are used in the water system to inhibit corrosion and deposition, such freshly produced iron (Fe.sup.+3) ion readily promotes coagulation of the polymer. Although the particular mechanism for such coagulation phenomenon is not known for certain, it is thought that the freshly produced Fe.sup.+3 ion, being small and highly charged, attracts the polymer causing coagulation thereof. This attractive force is exacerbated when anionic polymer electrolytes are used as the water treatment polymer.
In other words, when such freshly produced Fe.sup.+3 ions enter a water system, the resulting particulate iron oxides have a "fresh" (highly surface active) surface and are thus very active towards adsorption of polymers. In contrast, when iron ions are present in surface waters, they have been deactivated by the previous adsorption of various organic molecules, biopolymers, proteins etc. thereon. The available adsorption sites on these surface water iron ions are already occupied by these organics, and further adsorption is therefore precluded. The present invention is concerned with methods of inhibiting fouling and corrosion caused by the former "freshly produced Fe.sup.+3 ions".
I have found that the use of certain water soluble copolymers inhibits fouling and corrosion in test water systems under conditions which simulate those experienced when iron containing well water is used as a make-up water source. These water soluble copolymers, which shall be explained in greater detail hereinafter, may be referred to as (meth)acrylic acid type--allyl hydroxy propyl sulfonate ether water soluble copolymers.
These copolymers are not new per se as they have been reported in Japanese Patent Publication 58-9987. Indeed, they have been touted in such publication as being useful scale preventing agents when used in, inter alia, boilers, condensors, heat exchangers etc. and the disclosure also suggests use thereof in cooling water. However, this Japanese publication does not at all suggest that the disclosed polymers could be used in the specific environment herein required and claimed, to wit: use to inhibit corrosion and deposition in water systems having the previously described highly surface active iron ions existing therein.
Of arguably similar, although probably lesser interest, to the present invention is Japanese Patent Publication Sho No. 58-7415. Also mentioned as being of possible interest is Japanese Patent Publication No. 56-155692.